leetcode108 Convert Sorted Array to Binary Search Tree

"""
Given an array where elements are sorted in ascending order, convert it to a height balanced BST.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
Example:
Given the sorted array: [-10,-3,0,5,9],
One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:
      0
     / 
   -3   9
   /   /
 -10  5
"""
"""
对于二叉搜索树，左右结点的值有规律，应该想到递归
二分+递归解法
"""
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution:
    def sortedArrayToBST(self, nums):
        return self.convert(nums, 0, len(nums) - 1)

    def convert(self, nums, left, right):
        if left > right:  # bug 没写这个判断maximum recursion depth exceeded
            return None
        mid = (left + right) // 2
        Node = TreeNode(nums[mid])
        Node.left = self.convert(nums, left, mid - 1)
        Node.right = self.convert(nums, mid + 1, right)
        return Node